CVE-2023-34758

The current cryptography implementation in Sliver up to version 1.5.39 allows a MitM with access to the corresponding implant binary to execute arbitrary codes on implanted devices via intercepted and crafted responses. (Reserved CVE ID: CVE-2023-34758)

Details

Please see the PoC repo.

PoC

Please also see the PoC repo.
To setup a simple PoC environment,

1. Generate an implant with its C2 set to the PoC server's address and copy the embedded private implant key and public server key into the config json.
2. Run the implant on a separate VM and a notepad.exe window should pop up on the implanted VM.

References

https://github.com/BishopFox/sliver/blob/master/implant/sliver/cryptography/implant.go
https://github.com/BishopFox/sliver/blob/master/implant/sliver/cryptography/crypto.go
https://github.com/tangent65536/Slivjacker

Credits

Ting-Wei Hsieh from CHT Security Co. Ltd.

A successful attack grants the attacker permission to execute arbitrary code on the implanted device.

The application uses a cryptographic algorithm known to have weaknesses, such as MD5, SHA-1, or DES. Typical impact: compromised confidentiality or integrity of protected data.

CVE-2023-34758 has a CVSS score of 8.1 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.5.40); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2023-34758? CVE-2023-34758 is a critical-severity use of a broken or risky cryptographic algorithm vulnerability in github.com/bishopfox/sliver (go), affecting versions >= 1.5.0, < 1.5.40. It is fixed in 1.5.40. The application uses a cryptographic algorithm known to have weaknesses, such as MD5, SHA-1, or DES.
2. How severe is CVE-2023-34758? CVE-2023-34758 has a CVSS score of 8.1 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/bishopfox/sliver are affected by CVE-2023-34758? github.com/bishopfox/sliver (go) versions >= 1.5.0, < 1.5.40 is affected.
4. Is there a fix for CVE-2023-34758? Yes. CVE-2023-34758 is fixed in 1.5.40. Upgrade to this version or later.
5. Is CVE-2023-34758 exploitable, and should I be worried? Whether CVE-2023-34758 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2023-34758 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2023-34758? Upgrade github.com/bishopfox/sliver to 1.5.40 or later.