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Technical Analysis: How CVE-2026-41677 Works
The vulnerability stems from a lack of validation in the `_from_pem_callback` family of APIs. Specifically, when a user-provided password callback returns a length value, the function fails to check this returned length against the actual size of the destination buffer provided to it.
If a malicious or flawed callback returns a length larger than the buffer, OpenSSL will attempt to read that many bytes from the buffer. This causes an out-of-bounds read as the operation tries to access memory beyond the allocated buffer’s boundaries. This over-read can lead to a crash (Denial of Service) or expose sensitive information from adjacent memory.
The issue arises during the decryption of password-protected PEM files. The callback is responsible for providing a password. If the callback signals a password length that is too long, the underlying OpenSSL library over-reads the buffer instead of safely truncating. It is important to note that OpenSSL version 3.x contains internal mitigations for this issue and is not vulnerable.
DailyCVE Form
Platform: Rust-Openssl
Version: < 0.11.5
Vulnerability : Out-Of-Bounds Read
Severity: Low
Date: 2026-04-22
Prediction: 2026-05-15
What Undercode Say: Analytics
Search for the vulnerable dependency in your Cargo.lock grep -A 2 "name = \"openssl\"" Cargo.lock Check for usage of unsafe callback functions grep -r "set_password_callback" --include=".rs" . Real-time monitor for out-of-bounds memory access sudo perf record -e syscalls:sys_enter_read -ag -- sleep 30 sudo perf report
Exploit:
The exploit requires an attacker to either control the password callback logic (e.g., via a malicious dependency) or supply a crafted PEM file that triggers the oversized length return. The callback returns a `len` value exceeding the buffer capacity, causing OpenSSL to leak memory or crash.
Protection from this CVE
- Update to `openssl` crate version `0.11.5` or higher.
- For OpenSSL 1.1.1 or older, apply the patch to validate callback lengths before passing them to OpenSSL.
- Use OpenSSL 3.x or newer, which is not affected.
- Validate and sanitize all user-controlled inputs for password length.
Impact
1. Denial of Service through application crash.
- Potential leakage of adjacent memory contents, which could include sensitive data like private keys or session tokens.
3. Stability degradation in affected applications.
- Low severity due to memory leakage rather than arbitrary code execution.
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Sources:
Reported By: github.com
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