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VulnerabilityPublished

CVE-2026-114616: Authlib accepts an empty HMAC key, allowing JWS/JWT signature forgery (HS256/HS384/HS512)

Affects AuthlibSource GCVE Database

0
Authoritative record:CVE-2026-114616· High 7.4

Not known to be exploited · CVSS 7.4 High : upgrade to 1.9.1 soon.

Data as of 27 Oct 2026, 17:42 UTC

CVSS 3.1 base score
7.4High
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 1.9.1
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 22 Oct 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade Authlib to 1.9.1.

Affected software

ProductAffectedFixed in
PyPIAuthlibAffected
  • <1.9.1
Fixed in
  • 1.9.1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in Authlib version 1.9.1 that rejects empty HMAC keys. Users should upgrade to version 1.9.1 or later to remediate this vulnerability. Until upgraded, ensure that the HMAC key used for token verification is never empty or unset at runtime (e.g., avoid defaulting to empty strings from environment variables or configuration).

Description

Authlib versions up to 1.7.2 accept an empty HMAC key for JWS/JWT HS256/HS384/HS512 signature verification, allowing attackers to forge tokens with arbitrary claims. The empty key produces a deterministic digest that anyone can reproduce, bypassing signature verification. This vulnerability affects OAuth 2.0 resource servers and OIDC relying parties using Authlib if the verification key can be empty at runtime. The issue is fixed in Authlib 1.9.1.

References

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