GHSA-wvcv-832q-fjg7 is a high-severity (CVSS 7.5) CWE-326 vulnerability in tlslite-ng. 2 public exploit references exist, so weaponization risk is real. O3 Security confirms whether GHSA-wvcv-832q-fjg7 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
RSA weakness in tslite-ng
Real-World Exposure
tlslite-ngReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Impact
The code that performs decryption and padding check in RSA PKCS#1 v1.5 decryption is data dependant. In particular, code in current (as of 0.8.0-alpha38) master https://github.com/tlsfuzzer/tlslite-ng/blob/0812ed60860fa61a6573b2c0e18771414958f46d/tlslite/utils/rsakey.py#L407-L441 and code in 0.7.5 branch https://github.com/tlsfuzzer/tlslite-ng/blob/acdde3161124d6ae37c506b3476aea9996d12e97/tlslite/utils/rsakey.py#L394-L425 has multiple ways in which it leaks information (for one, it aborts as soon as the plaintext doesn't start with 0x00, 0x02) about the decrypted ciphertext (both the bit length of the decrypted message as well as where the first unexpected byte lays).
All TLS servers that enable RSA key exchange as well as applications that use the RSA decryption API directly are vulnerable.
All previous versions of tlslite-ng are vulnerable.
Patches
The patches to fix it are proposed in https://github.com/tlsfuzzer/tlslite-ng/pull/438 https://github.com/tlsfuzzer/tlslite-ng/pull/439
Note: the patches depend on Python processing the individual bytes in side-channel free manner, this is known to not be the case: https://securitypitfalls.wordpress.com/2018/08/03/constant-time-compare-in-python/ As such, users that require side-channel resistance are recommended to use different TLS implementations, as stated in the security policy of tlslite-ng.
Workarounds
There is no way to workaround this issue.
References
https://securitypitfalls.wordpress.com/2018/08/03/constant-time-compare-in-python/
For more information
If you have any questions or comments about this advisory please open an issue in tlslite-ng.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | tlslite-ng | all versions | 0.7.6 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for tlslite-ng. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update tlslite-ng to 0.7.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-wvcv-832q-fjg7 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-wvcv-832q-fjg7 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-wvcv-832q-fjg7. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-wvcv-832q-fjg7 in your dependencies?
O3 detects GHSA-wvcv-832q-fjg7 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.