CVE-2018-10903
A flaw was found in python-cryptography versions between >=1.9.0 and <2.3. The finalize_with_tag API did not enforce a minimum tag length.…
- 7.5HighCVSS base score
- 3.2%Exploitation in 30 daysEPSS · top 12% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
A flaw was found in python-cryptography versions between >=1.9.0 and <2.3. The finalize_with_tag API did not enforce a minimum tag length. If a user did not validate the input length prior to passing it to finalize_with_tag an attacker could craft an invalid payload with a shortened tag (e.g. 1 byte) such that they would have a 1 in 256 chance of passing the MAC check. GCM tag forgeries can cause key leakage.
Timeline
ID reserved
By redhat
- 3 months later
· 3 months later
Published
- 6 years later
· 6 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| redhatCNA (assigner) | 3.0 | High7.5 | CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N |
| NVDNVD · Modified | 3.0 | High7.5 | CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N |
- EPSS (exploitation in 30 days)
- 3.2% · top 12% of all CVEs (11 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.
Affected products
[UNKNOWN] · python-cryptography
- affected 2.3
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- PyPIcryptographyGHSA-fcf9-3qw3-gxmj (opens in a new tab)
References
References4
- RHSA-2018:3600 (opens in a new tab)vendor-advisoryx_refsource_REDHATx_transferred
- USN-3720-1 (opens in a new tab)vendor-advisoryx_refsource_UBUNTUx_transferred
- https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-10903 (opens in a new tab)x_refsource_CONFIRMx_transferred
- https://github.com/pyca/cryptography/pull/4342/commits/688e0f673bfbf43fa898994326c6877f00ab19ef (opens in a new tab)x_refsource_CONFIRMx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2018-0030 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-fcf9-3qw3-gxmj (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2018-10903)Record last updated .