CVE-2026-54355

MEDIUMPre-NVD 5.35.3
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This medium-severity CVE scores 5.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5% (42nd percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
Elevated

Also known asEUVD-2026-82433 (ENISA EUVD)Source: ENISA EUVD

5.3EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 5.3Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

MapServer is a system for developing web-based GIS applications. From 6.0 until 8.6.4, MapServer's OpenLayers HTML output for SERVICE=WMS&REQUEST=GetMap&FORMAT=application/openlayers reflects an attacker-controlled X-Forwarded-Host value received as HTTP_X_FORWARDED_HOST through msBuildOnlineResource(), processLine(), and the [mapserv_onlineresource] substitution in src/maputil.c and src/maptemplate.c without escaping it for a single-quoted JavaScript string. When the deployment trusts the forwarded header and does not configure a fixed ows_onlineresource or MS_ONLINERESOURCE value, embedded single quotes can escape the generated URL string. An unauthenticated attacker can craft a URL that executes arbitrary JavaScript in the MapServer site origin when opened by a victim, enabling access to sessions or tokens, same-origin data and requests, and actions as the victim. This issue is fixed in version 8.6.4.

CVSS v3
5.3
EG Score
5.3MEDIUMmedium confidence
EG Risk
40
EG Risk 40/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity53% × 45%
Impact severity (EG Severity): CVSS 5.3 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.5%
EPSS %ILE
42nd
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (5.3): severity, escalated by confirmed exploitation. This CVE's 5.3 is its impact severity (EG Severity), not escalated.

EG Severity
5.3 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source · CVSS v3.0 or v3.1
EG Likelihood
0.5% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-24). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

September 17, 2026

Last Modified

September 30, 2026

Advisory Details (7)

Auto-updated Sep 17, 2026
Patch available. Sources: github_pr, github_commit, github_release, github.
Web page

MapServer 8.6 Changelog — MapServer 8.6.6 documentation

https://mapserver.org/development/changelog/changelog-8-6.html#changelog-8-6
GitHub release Patch Available

MapServer 8.6.4

Patch available: MapServer/MapServer rel-8-6-4

https://github.com/MapServer/MapServer/releases/tag/rel-8-6-4
GitHub commit Patch Available

commit ff17ef190caa (MapServer/MapServer)

Patch available: MapServer/MapServer rel-8-6-4 (contains commit ff17ef190caa)

https://github.com/MapServer/MapServer/commit/ff17ef190caaeaa9002ac3d1c7969ec5315c345e
GitHub commit

commit edc1033c7963 (MapServer/MapServer)

Fix landed in MapServer/MapServer commit edc1033c7963 — awaiting tagged release

https://github.com/MapServer/MapServer/commit/edc1033c7963fcffd160d85cf430f49aaf4a1374
GitHub pull request Patch Available

[Backport branch-8-6] WMS OpenLayers output: properly escape mapserv_onlineresource

Patch available: MapServer/MapServer rel-8-6-4 (PR #7518 merged 2026-06-01)

https://github.com/MapServer/MapServer/pull/7518
GitHub pull request

WMS OpenLayers output: properly escape mapserv_onlineresource

Fix merged in MapServer/MapServer PR #7517 on 2026-05-31 — awaiting tagged release

https://github.com/MapServer/MapServer/pull/7517
GitHub advisoryMentions a patch (unverified)

MapServer 8.6.3: Reflected XSS in OpenLayers HTML Output via `HTTP_X_FORWARDED_HOST` · Advisory · MapServer/MapServer · GitHub

https://github.com/MapServer/MapServer/security/advisories/GHSA-xqj6-vjqr-33vv

Affected Packages

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
mapserver8.0.0-3 ... 8.6.6-1~bpo13+1 (53 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
mapserver8.4.0-4 ... 8.6.6-1~bpo13+1 (23 versions)
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
mapserver8.4.0-4 ... 8.6.4-1~bpo13+1 (16 versions)
  • every version up to 8.6.4-1: fixed in 8.6.4-1
—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 8× in last 7d / 45× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

  1. 2026-11-02 16:45 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  2. 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  3. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  4. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  5. 2026-10-30 11:25 UTCOSV refresh
  6. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  7. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  8. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  9. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  10. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  11. 2026-10-25 14:19 UTCEG score recompute
  12. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  13. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  14. 2026-10-22 21:21 UTCEG score recompute
  15. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  16. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  17. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  18. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  19. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  20. 2026-10-18 03:31 UTCEG score recompute
  21. 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  22. 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  23. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  24. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  25. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.5% · 41st percentile
Show 50 more
  1. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  2. 2026-10-12 15:56 UTCEG score recompute
  3. 2026-10-11 19:39 UTCEG score recompute
  4. 2026-10-11 16:54 UTCEG score recompute
  5. 2026-10-11 14:18 UTCEG score recompute
  6. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  7. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  8. 2026-10-10 15:46 UTCEG score recompute
  9. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  10. 2026-10-09 13:24 UTCEG score recompute
  11. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  12. 2026-10-08 10:15 UTCEG score recompute
  13. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  14. 2026-10-07 07:54 UTCEG score recompute
  15. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  16. 2026-10-06 05:34 UTCEG score recompute
  17. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  18. 2026-10-05 03:07 UTCEG score recompute
  19. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  20. 2026-10-04 00:29 UTCEG score recompute
  21. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  22. 2026-10-02 22:09 UTCEG score recompute
  23. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  24. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  25. 2026-09-30 17:27 UTCEG score recompute
  26. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  27. 2026-09-30 09:08 UTCEG score recompute
  28. 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  29. 2026-09-29 06:45 UTCEG score recompute
  30. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  31. 2026-09-28 04:26 UTCEG score recompute
  32. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  33. 2026-09-27 02:06 UTCEG score recompute
  34. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  35. 2026-09-25 23:47 UTCEG score recompute
  36. 2026-09-24 21:24 UTCEG score recompute
  37. 2026-09-24 20:57 UTCEG score recompute
  38. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  39. 2026-09-24 11:18 UTCEG score recompute
  40. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  41. 2026-09-23 08:59 UTCEG score recompute
  42. 2026-09-22 06:39 UTCEG score recompute
  43. 2026-09-21 04:19 UTCEG score recompute
  44. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  45. 2026-09-20 01:59 UTCEG score recompute
  46. 2026-09-18 23:39 UTCEG score recompute
  47. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  48. 2026-09-17 21:20 UTCEG score recompute
  49. 2026-09-17 20:34 UTCEG score recomputeFirst assessed: 5.3 MEDIUM
  50. 2026-09-17 20:34 UTCMITRE cvelistV5first tracked

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2026-54355?
CVE-2026-54355 is a medium-severity vulnerability; its CVE record was published on September 17, 2026. MapServer is a system for developing web-based GIS applications. From 6.0 until 8.6.4, MapServer's OpenLayers HTML output for SERVICE=WMS&REQUEST=GetMap&FORMAT=application/openlayers reflects an attacker-controlled X-Forwarded-Host value received as HTTP_X_FORWARDED_HOST through…
When was the CVE record for CVE-2026-54355 published?
The CVE record for CVE-2026-54355 was published on September 17, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of September 30, 2026; the record at its source may have been updated since.
Is CVE-2026-54355 actively exploited?
CVE-2026-54355 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (42nd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-54355?
CVE-2026-54355 has a CVSS base score of 5.3 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-54355?
A fix for CVE-2026-54355 is available: update to the fixed version the vendor names in its advisory.

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