Vulnerability in tlslite-ng (CVE-2020-26263)
Summary
Vulnerability in tlslite-ng (CVE-2020-26263). Data can be tampered with by attackers. Mitigation: upgrade to 0.7.6 or later.
Original description
The description as published by the source.
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…
Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2020-26263 has been found in tlslite-ng.
Data can be tampered with by attackers.
What to do: upgrade tlslite-ng to 0.7.6 or later.
If unsure, ask your IT team or search "tlslite-ng CVE-2020-26263" on the vendor's site.
CVE-2020-26263 (tlslite-ng) — CWE-326
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 0.7.6 — apply immediately
Workaround: There is no way to workaround this issue.
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-326) exists in tlslite-ng.
Check the vendor advisory for the affected versions of tlslite-ng.
Severity: ?. Data can be tampered with by attackers.
Update to 0.7.6.
Workaround: There is no way to workaround this issue.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'tlslite-ng' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'tlslite-ng' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
tlslite-ngを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply temporary workaround mitigate
There is no way to workaround this issue.パッチが適用されるまでの応急処置として、There is no way to workaround this issue. を実施。回避策の副作用 (機能低下) を確認した上で。
-
3Apply patch patch
Upgrade tlslite-ng to 0.7.6ステージング環境で 0.7.6 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
4Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory nvd.nist.gov
- package github.com
- web github.com
- web github.com
- web github.com
- web github.com
- web github.com
- web pypi.org
- web securitypitfalls.wordpress.com