Issue summary: Converting an excessively large OCTET STRING value to a hexadecimal string leads to a heap buffer overflow on 32 bit platforms.
Impact summary: A heap buffer overflow may lead to a crash or possibly an attacker controlled code execution or other undefined behavior.
If an attacker can supply a crafted X.509 certificate with an excessively large OCTET STRING value in extensions such as the Subject Key Identifier (SKID) or Authority Key Identifier (AKID) which are being converted to hex, the size of the buffer needed for the result is calculated as multiplication of the input length by 3. On 32 bit platforms, this multiplication may overflow resulting in the allocation of a smaller buffer and a heap buffer overflow.
Applications and services that print or log contents of untrusted X.509 certificates are vulnerable to this issue. As the certificates would have to have sizes of over 1 Gigabyte, printing or logging such certificates is a fairly unlikely operation and only 32 bit platforms are affected, this issue was assigned Low severity.
The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.
Weakness
The product writes data past the end, or before the beginning, of the intended buffer.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Openssl | Openssl | 3.0.0 (including) | 3.0.20 (excluding) |
| Openssl | Openssl | 3.3.0 (including) | 3.3.7 (excluding) |
| Openssl | Openssl | 3.4.0 (including) | 3.4.5 (excluding) |
| Openssl | Openssl | 3.5.0 (including) | 3.5.6 (excluding) |
| Openssl | Openssl | 3.6.0 (including) | 3.6.2 (excluding) |
| Red Hat Hardened Images | RedHat | openssl-main-3.5.6-0.1.hum1 | * |
| Edk2 | Ubuntu | devel | * |
| Edk2 | Ubuntu | noble | * |
| Edk2 | Ubuntu | questing | * |
| Edk2 | Ubuntu | resolute | * |
| Openssl | Ubuntu | devel | * |
| Openssl | Ubuntu | jammy | * |
| Openssl | Ubuntu | noble | * |
| Openssl | Ubuntu | questing | * |
| Openssl | Ubuntu | resolute | * |
| Openssl | Ubuntu | upstream | * |
Potential Mitigations
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer.
Be wary that a language’s interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Examples include the Safe C String Library (SafeStr) by Messier and Viega [REF-57], and the Strsafe.h library from Microsoft [REF-56]. These libraries provide safer versions of overflow-prone string-handling functions.
Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.
D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.
Consider adhering to the following rules when allocating and managing an application’s memory:
Run or compile the software using features or extensions that randomly arrange the positions of a program’s executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.
Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as “rebasing” (for Windows) and “prelinking” (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.
For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].
Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX [REF-60] [REF-61]. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment.
For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND [REF-1336].
References
- https://github.com/openssl/openssl/commit/364f095b80601db632b0def6a33316967f863bde
- https://github.com/openssl/openssl/commit/7a9087efd769f362ad9c0e30c7baaa6bbfa65ecf
- https://github.com/openssl/openssl/commit/945b935ac66cc7f1a41f1b849c7c25adb5351f49
- https://github.com/openssl/openssl/commit/a24216018e1ede8ff01a4ff5afff7dfbd443e2f9
- https://github.com/openssl/openssl/commit/a91e537d16d74050dbde50bb0dfb1fe9930f0521
- https://openssl-library.org/news/secadv/20260407.txt
- https://cert-portal.siemens.com/productcert/html/ssa-032379.html