tlslite-ng off-by-one error on mac checking

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.2 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2018-1000159: 0.77% estimated exploitation activity in the next 30 days; percentile 55.74 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

tlslite-ng version 0.7.3 and earlier, since commit d7b288316bca7bcdd082e6ccff5491e241305233 contains a CWE-354: Improper Validation of Integrity Check Value vulnerability in TLS implementation, tlslite/utils/constanttime.py: ctcheckcbcmacandpad(); line endpos = datalen - 1 - mac.digestsize that can result in an attacker manipulating the TLS ciphertext which will not be detected by receiving tlslite-ng. This attack appears to be exploitable via man in the middle on a network connection. This vulnerability appears to have been fixed after commit 3674815d1b0f7484454995e2737a352e0a6a93d8.

Published by the source

12 Jul 2018, 20:30 UTC

Last modified by the source

24 Nov 2024, 05:38 UTC

Source last checked

26 Oct 2026, 13:26 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-cwh5-3cw7-4286

2. Revision 2 · amended · 24 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-cwh5-3cw7-4286

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# Patch Next advisory brief: CVE-2018-1000159

Advisory: tlslite-ng off-by-one error on mac checking
IDs: CVE-2018-1000159, GHSA-cwh5-3cw7-4286
Record: https://patchnext.com/advisories/cve-2018-1000159 (revision 3, source checked 26 Oct 2026, 13:26 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: tlslite-ng 0.7.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI tlslite-ng: affected < 0.7.4; fixed in 0.7.4

## Suggested inspection (read-only)
- `python -m pip show tlslite-ng`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on tlslite-ng.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-cwh5-3cw7-4286 (OSV record GHSA-cwh5-3cw7-4286 lists affected ranges: PyPI tlslite-ng >=0 <0.7.4 (fixed))
- Verified: https://github.com/advisories/GHSA-cwh5-3cw7-4286 (GitHub-reviewed advisory GHSA-cwh5-3cw7-4286 lists affected ranges: PyPI tlslite-ng >=0 <0.7.4)

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