CVE-2026-49265

MEDIUMPre-NVD 6.86.8
EchelonGraph scoreMEDIUM confidence

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

Score 6.8 from GitHub Security Advisory (severity: MODERATE) published 2026-09-29. A secondary CVSS source baseline 6.8; 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 week

Also known asEUVD-2026-98833 (ENISA EUVD) · GHSA-xpv3-w29h-x7cv (GitHub Security Advisories) · PYSEC-2026-4114 (OSV.dev)Source: ENISA EUVD

6.8EG
EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 6.8Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

OAuthLib is an implementation of the OAuth request-signing logic for Python 3.6+. From 3.0.0 until 4.0.0, OAuthLib's PKCE checks in oauthlib/oauth2/rfc6749/grant_types/authorization_code.py compare attacker-supplied code_verifier values with stored challenges using ordinary string equality in code_challenge_method_plain and code_challenge_method_s256. Because the comparison can return after a length difference or the first mismatching character, repeated token endpoint measurements can reveal common-prefix timing information that could potentially allow recovery of the code_verifier, unauthorized access-token acquisition, and account takeover. Practical exploitation requires an intercepted, single-use authorization code and enough measurements to overcome real-world network noise; the local timing benchmark does not establish practical remote account takeover, so the weakness remains a defense-in-depth concern. This issue is fixed in version 4.0.0.

CVSS v3
6.8
EG Score
6.8MEDIUMmedium confidence
EG Risk
31
EG Risk 31/100

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)
Severity68% × 45%
Impact severity (EG Severity): CVSS 6.8 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.2% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
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 none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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
0.2%
EPSS %ILE
15th
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 (6.8): severity, escalated by confirmed exploitation. This CVE's 6.8 is its impact severity (EG Severity), not escalated.

EG Severity
6.8 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.2% 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: 14 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 none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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)14 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 total (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 29, 2026

Last Modified

October 16, 2026

Advisory Details (5)

Auto-updated Oct 13, 2026
🔬 Proof of concept available. Patch available. Sources: github_pr, github_commit, github_release, github.
Web page🟡 PoC Available

advisory-database/vulns/oauthlib/PYSEC-2026-4114.yaml at main · pypa/advisory-database · GitHub

https://github.com/pypa/advisory-database/tree/main/vulns/oauthlib/PYSEC-2026-4114.yaml
GitHub release Patch Available

4.0.0

Patch available: oauthlib/oauthlib v4.0.0

https://github.com/oauthlib/oauthlib/releases/tag/v4.0.0
GitHub commit Patch Available

commit 74664d3fe037 (oauthlib/oauthlib)

Patch available: oauthlib/oauthlib v4.0.0 (contains commit 74664d3fe037)

https://github.com/oauthlib/oauthlib/commit/74664d3fe037a354e180e305135c6bab1747a6b0
GitHub pull request Patch Available

Improve PKCE code comparison

Patch available: oauthlib/oauthlib v4.0.0 (PR #963 merged 2026-07-14)

https://github.com/oauthlib/oauthlib/pull/963
GitHub advisoryMentions a patch (unverified)

Timing Attack Vulnerability in PKCE code_verifier Comparison (CWE-208) · Advisory · oauthlib/oauthlib · GitHub

https://github.com/oauthlib/oauthlib/security/advisories/GHSA-xpv3-w29h-x7cv

Vendor Advisories for CVE-2026-49265(6)

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

Patch Availability(3)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhatrhaii/vllm-cpu-rhel9:17914736142026-10-13redhat
redhatrhaii/vllm-cuda-rhel9:17914736312026-10-13redhat
pipoauthlib @ 4.0.0 (fixes >= 3.0.0, < 4.0.0)—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)
PyPI(1)
PackageVulnerable rangeFix by version rangeDependents
oauthlib3.0.0 ... 3.3.1 (10 versions)
  • 3.0.0 up to 4.0.0: fixed in 4.0.0
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 9× in last 7d / 31× 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. 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.2% · 15th percentile
  2. 2026-11-01 07:46 UTCGHSA enrichmentGHSA-xpv3-w29h-x7cv · GitHub severity MODERATE · GitHub CVSS 6.8
  3. 2026-11-01 07:46 UTCEG score recompute
  4. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.2% · 15th percentile
  5. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.2% · 15th percentile
  6. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.2% · 15th percentile
  7. 2026-10-28 02:25 UTCOSV refresh
  8. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.2% · 15th percentile
  9. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.2% · 15th percentile
  10. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.2% · 15th percentile
  11. 2026-10-25 14:22 UTCEG score recompute
  12. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  13. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  14. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  15. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  16. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  17. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  18. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  19. 2026-10-18 03:34 UTCEG score recompute
  20. 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  21. 2026-10-16 20:12 UTCEG score recompute
  22. 2026-10-16 20:12 UTCVendor advisory
  23. 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  24. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  25. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.4% · 29th percentile
Show 7 more
  1. 2026-10-13 17:29 UTCEG score recompute
  2. 2026-10-13 16:30 UTCEG score recompute
  3. 2026-10-12 16:00 UTCEG score recompute
  4. 2026-10-11 19:43 UTCEG score recompute
  5. 2026-10-11 16:57 UTCEG score recompute
  6. 2026-10-11 14:21 UTCEG score recompute
  7. 2026-09-29 18:23 UTCEG score recomputeFirst assessed: 6.8 MEDIUM

Related CVEs(same product + same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-49265?
CVE-2026-49265 is a medium-severity vulnerability; its CVE record was published on September 29, 2026. OAuthLib is an implementation of the OAuth request-signing logic for Python 3.6+. From 3.0.0 until 4.0.0, OAuthLib's PKCE checks in oauthlib/oauth2/rfc6749/grant_types/authorization_code.py compare attacker-supplied code_verifier values with stored challenges using ordinary string equality in…
When was the CVE record for CVE-2026-49265 published?
The CVE record for CVE-2026-49265 was published on September 29, 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 16, 2026; the record at its source may have been updated since.
Is CVE-2026-49265 actively exploited?
CVE-2026-49265 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (15th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-49265?
CVE-2026-49265 has a CVSS base score of 6.8 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-49265?
A fix for CVE-2026-49265 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-49265 are linked in the Vendor Advisories panel on this page.

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