CVE-2026-113799

MEDIUMPre-NVD 5.35.3
EchelonGraph scoreHIGH confidence

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

Score 5.3 from GitHub Security Advisory (severity: MODERATE) published 2026-10-21. A secondary CVSS source baseline 5.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source
Trending — 4 sources updated this weekElevated

Also known asEUVD-2026-107388 (ENISA EUVD) · GHSA-26w4-8w32-4x3v (GitHub Security Advisories)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: 0.4%CVSS: 5.3Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

Slack Morphism is a client library for Slack Web/Events API/Socket Mode and Block Kit. Versions 1.0.0 through 2.27.0 expose the correct Slack request HMAC when signature verification fails. For an invalid request, slack-morphism computes the correct signature for the attacker-controlled timestamp and request body and stores it in SlackEventWrongSignatureError.generated_hash. The error's Debug and Display representations expose that value, and the default Axum listener error handler logs it at error level. An attacker who can both reach the application's Slack callback endpoint and read its application/service logs can therefore use the verifier as a chosen-message HMAC oracle. The attacker can send an arbitrary request with an invalid signature, recover the correct signature from the resulting log entry, and resend the same request within the five-minute freshness window. The second request passes Slack Morphism's signature verification and reaches the protected application callback without the attacker knowing the Slack signing secret. Version 2.28.0 patches the issue.

CVSS v3
5.3
EG Score
5.3MEDIUMhigh 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
0.4%
EPSS %ILE
37th
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.GitHub Security Advisory CVSS
EG Likelihood
0.4% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-31). 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

October 21, 2026

Last Modified

October 30, 2026

Advisory Details (4)

Auto-updated Oct 22, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github_pr, github_release, github.
GitHub advisoryMentions a patch (unverified)🟡 PoC Available

Slack Morphism verifier errors disclose valid HMACs in the logs · Advisory · abdolence/slack-morphism-rust · GitHub

https://github.com/abdolence/slack-morphism-rust/security/advisories/GHSA-26w4-8w32-4x3v
GitHub release Patch Available

v2.28.0

Patch available: abdolence/slack-morphism-rust v2.28.0

https://github.com/abdolence/slack-morphism-rust/releases/tag/v2.28.0
GitHub pull request Patch Available

fix: Do not expose request signatures in verifier errors

Patch available: abdolence/slack-morphism-rust v2.28.0 (PR #387 merged 2026-09-09)

https://github.com/abdolence/slack-morphism-rust/pull/387
GitHub commit Patch Available

commit ac95d0d4539d (abdolence/slack-morphism-rust)

Patch available: abdolence/slack-morphism-rust v2.28.0 (contains commit ac95d0d4539d)

https://github.com/abdolence/slack-morphism-rust/commit/ac95d0d4539d0eac548a8db99c51c0c1ae832756

Vendor Advisories for CVE-2026-113799(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(1)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
rustslack-morphism @ 2.28.0 (fixes >= 1.0.0, <= 2.27.0)—ghsa

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(1 across 1 ecosystem)
crates.io(1)
PackageVulnerable rangeFix by version rangeDependents
slack-morphism—
  • 1.0.0 up to 2.28.0: fixed in 2.28.0
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 13× in last 7d / 23× 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 16:44 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  2. 2026-11-01 16:33 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  3. 2026-11-01 07:59 UTCGHSA enrichmentGHSA-26w4-8w32-4x3v · GitHub severity MODERATE · GitHub CVSS 5.3
  4. 2026-11-01 07:59 UTCEG score recompute
  5. 2026-10-31 16:32 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  6. 2026-10-30 16:33 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  7. 2026-10-30 16:27 UTCEG score recompute
  8. 2026-10-30 15:26 UTCEG score recompute
  9. 2026-10-30 15:20 UTCEG score recompute
  10. 2026-10-30 03:55 UTCOSV refresh
  11. 2026-10-29 16:32 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  12. 2026-10-28 16:31 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  13. 2026-10-27 16:31 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  14. 2026-10-26 16:30 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  15. 2026-10-25 16:32 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  16. 2026-10-25 14:51 UTCEG score recompute
  17. 2026-10-24 16:32 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  18. 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  19. 2026-10-22 17:50 UTCEG score recompute
  20. 2026-10-22 16:33 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  21. 2026-10-21 17:27 UTCEG score recompute
  22. 2026-10-21 16:27 UTCEG score recomputeFirst assessed: 5.3 MEDIUM
  23. 2026-10-21 16:25 UTCMITRE cvelistV5first tracked

Related CVEs(same product + same CWE)

Same product

2 shown

crates.io:slack-morphism

Frequently asked(5)

What is CVE-2026-113799?
CVE-2026-113799 is a medium-severity vulnerability; its CVE record was published on October 21, 2026. Slack Morphism is a client library for Slack Web/Events API/Socket Mode and Block Kit. Versions 1.0.0 through 2.27.0 expose the correct Slack request HMAC when signature verification fails. For an invalid request, slack-morphism computes the correct signature for the attacker-controlled timestamp…
When was the CVE record for CVE-2026-113799 published?
The CVE record for CVE-2026-113799 was published on October 21, 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 October 30, 2026; the record at its source may have been updated since.
Is CVE-2026-113799 actively exploited?
CVE-2026-113799 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (37th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-113799?
CVE-2026-113799 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-2026-113799?
A fix for CVE-2026-113799 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-113799 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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