GHSA-423w-p2w9-r7vq
MEDIUMAEADs/aes-gcm: Plaintext exposed in decrypt_in_place_detached even on tag verification failure
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
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Description
Summary
In the AES GCM implementation of decrypt_in_place_detached, the decrypted ciphertext (i.e. the correct plaintext) is exposed even if tag verification fails.
Impact
If a program using the aes-gcm crate's decrypt_in_place* APIs accesses the buffer after decryption failure, it will contain a decryption of an unauthenticated input. Depending on the specific nature of the program this may enable Chosen Ciphertext Attacks (CCAs) which can cause a catastrophic breakage of the cipher including full plaintext recovery.
Details
As seen in the implementation of decrypt_in_place_detached for AES GCM, if the tag verification fails, an error is returned. Because the decryption of the ciphertext is done in place, the plaintext contents are now exposed via buffer.
This should ideally not be the case - as noted in page 17 of NIST's publication Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC: In Step 8, the result of Step 7 is compared with the authentication tag that was received as an input: if they are identical, then the plaintext is returned; otherwise,FAIL is returned.
This is seems correctly addressed in the AES GCM SIV implementation, where the decrypted buffer is encrypted again before the error is returned - this fix is straightforward to implement in AES GCM. To ensure that these types of cases are covered during testing, it would be valuable to add test cases like 23, 24 etc from project wycheproof to ensure that when a bad tag is used, there is an error on decryption and that the plaintext value is not exposed.
PoC
To reproduce this issue, I'm using test case 23 from project wycheproof.
let key = GenericArray::from_slice(&hex!("000102030405060708090a0b0c0d0e0f"));
let nonce = GenericArray::from_slice(&hex!("505152535455565758595a5b"));
let tag = GenericArray::from_slice(&hex!("d9847dbc326a06e988c77ad3863e6083")); // bad tag
let mut ct = hex!("eb156d081ed6b6b55f4612f021d87b39");
let msg = hex!("202122232425262728292a2b2c2d2e2f");
let aad = hex!("");
let cipher = Aes128Gcm::new(&key);
let _plaintext = cipher.decrypt_in_place_detached(&nonce, &aad, &mut ct, &tag);
assert_eq!(ct, msg);
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | aes-gcm | ≥ 0.10.0&&< 0.10.3 | 0.10.3 |
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 aes-gcm. 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 aes-gcm to 0.10.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-423w-p2w9-r7vq 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-423w-p2w9-r7vq 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-423w-p2w9-r7vq. 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-423w-p2w9-r7vq in your dependencies?
O3 detects GHSA-423w-p2w9-r7vq across crates.io dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.