Quick answer
Direct answer
Risk scores
| CVSS metric | What it means |
|---|---|
| Attack vector (AV:N) | Network: reachable remotely |
| Attack complexity (AC:L) | Low complexity |
| Attack requirements (AT:P) | Attack requirements present |
| Privileges required (PR:N) | No privileges required |
| User interaction (UI:N) | No user interaction |
| Confidentiality (VC:H) | High confidentiality impact |
| Integrity (VI:H) | High integrity impact |
| Availability (VA:H) | High availability impact |
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
About Rust-Openssl Project Rust-Openssl
CVE-2026-41676 affects Rust-Openssl Project Rust-Openssl, a product from Rust-Openssl Project. Before acting, confirm where Rust-Openssl Project Rust-Openssl runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.
What the flaw is
In plain terms: rust-openssl provides OpenSSL bindings for the Rust programming language. From 0.9.27 to before 0.10.78, Deriver::derive (and PkeyCtxRef::derive) sets len = buf.len() and passes it as the in/out length to EVP_PKEY_derive, relying on OpenSSL to honor it. On OpenSSL 1.1.x, X25519, X448, DH and HKDF-extract ignore the incoming *keylen, unconditionally writing the full shared secret (32/56/prime-size bytes). A caller passing a short slice gets a heap/stack overflow from safe code. OpenSSL 3.x providers do check, so this only impacts older OpenSSL. This vulnerability is fixed in 0.10.78.
The weakness class is Out of Bounds Write. The program writes past the end of a buffer, a common path to code execution.
Based on its CVSS vector, the flaw can be reached over the network, needs no login, and needs no user interaction. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Affected versions and timeline
| Field | Detail |
|---|---|
| Product | Rust-Openssl Project Rust-Openssl |
| Affected versions | Rust-Openssl from 0.9.27 before 0.10.78 |
| Published | Apr 24, 2026 |
| Last modified | Jul 15, 2026 |
| Added to CISA KEV | Not listed |
| Assigning CNA | security-advisories@github.com |
How to detect it
- Inventory every instance of Rust-Openssl Project Rust-Openssl and record the running version against the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
- Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.
How to fix it
- Apply the fixed version of Rust-Openssl Project Rust-Openssl named in the vendor advisory.
- If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
- Rescan after the change to prove the exposure is gone, then close the ticket.
CTEM action plan
| CTEM stage | What to do for this CVE |
|---|---|
| Scope | Add every business service that depends on Rust-Openssl Project Rust-Openssl to the current CTEM cycle. |
| Discover | Find all instances, including shadow and cloud deployments, and record versions and exposure. |
| Prioritize | Rank using EPSS and CVSS together with asset exposure and business impact. |
| Validate | Confirm the flaw is reachable and exploitable in your environment and that compensating controls work. |
| Mobilize | Assign the fix to the asset owner with a due date matched to the priority, then verify closure. |
CWE References
- CWE-131 More CVEs with this weakness
- CWE-787: Out of Bounds Write More CVEs with this weakness
Technical References
Frequently asked questions
Related CVEs
rust-openssl provides OpenSSL bindings for the Rust programming language. From 0.10.39 to before 0.10.78, EVP_DigestFinal() always writes EVP_MD_CTX_size(ctx) to the out buffer. If out is smaller than that, MdCtxRef::digest_final() writes past its end, usually corrupting the stack. This is reachable from safe Rust. This vulnerability is fixed in 0.10.78.
rust-openssl provides OpenSSL bindings for the Rust programming language. From to before 0.10.78, aes::unwrap_key() contains an incorrect assertion: it checks that out.len() + 8 <= in_.len(), but this condition is reversed. The intended invariant is out.len() >= in_.len() - 8, ensuring the output buffer is large enough. Because of the inverted check, the function only accepts buffers at or below the minimum required size and rejects larger ones. If a smaller buffer is provided the function will write past the end of out by in_.len() - 8 - out.len() bytes, causing an out-of-bounds write from a safe public function. This vulnerability is fixed in 0.10.78.
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NLnet Labs Unbound 1.14.0 up to and including version 1.25.0 has a vulnerability that results in heap overflow when encoding multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options in the reply packet. The relevant options ('nsid', 'answer-cookie', 'pad-responses' (default)) need to be enabled for the vulnerability to be exploited. An adversary who can query Unbound can exploit the vulnerability by attaching multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options to the query. A flaw in the size calculation of the EDNS field truncates the correct value which allows the encoder to overflow the available space when writing. Those two combined lead to a heap overflow write of Unbound controlled data and eventually a crash. Unbound 1.25.1 contains a patch with a fix to de-duplicate the EDNS options and a fix to prevent truncation of the EDNS field size calculation.
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