CVE-2023-26556: io.finnet tss-lib before 2.0.0 can leak a secret key via a timing side-channel attack because it relies on the

Q: How do I fix CVE-2023-26556?

tss-lib: upgrade to 2.0.0. Exact commands for each OS are on this page.

Q: Is CVE-2023-26556 being exploited?

CVE-2023-26556 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2023-26556 affect?

CVE-2023-26556 affects tss-lib. Severity is critical (CVSS 9.1). io.finnet tss-lib before 2.0.0 can leak a secret key via a timing side-channel attack because it relies on the scalar-multiplication implementation in Go crypto/elliptic, which is not constant time (there is an if statement in a loop). One

Q: How urgent is CVE-2023-26556?

Priority 51/100. Critical severity; Remotely exploitable, no login, no user action

This month

CRITICAL 9.1REMOTEUPGRADE

CVE-2023-26556 is a critical-severity flaw (CVSS 9.1) affecting tss-lib. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

io.finnet tss-lib before 2.0.0 can leak a secret key via a timing side-channel attack because it relies on the scalar-multiplication implementation in Go crypto/elliptic, which is not constant time (there is an if statement in a loop). One leak is in ecdsa/keygen/round_2.go. (bnb-chain/tss-lib and thorchain/tss are also affected.)

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.9% (top 41%)
CISA exploited list	No
Weakness	CWE-203
Published	2023-04-21
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: iofinnet

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2023-04-21 18:15 UTCPublished CVE record published
2026-06-17 05:43 UTCUpdated Record last modified

iofinnet tss-lib UPGRADE

Affected: < 2.0.0

Fixed in: 2.0.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy tss-lib || rpm -q tss-lib || tss-lib --version

2. UPGRADE to 2.0.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade tss-lib

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade tss-lib

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2023-26556?

tss-lib: upgrade to 2.0.0. Exact commands for each OS are on this page.

Is CVE-2023-26556 being exploited?

CVE-2023-26556 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2023-26556 affect?

CVE-2023-26556 affects tss-lib. Severity is critical (CVSS 9.1). io.finnet tss-lib before 2.0.0 can leak a secret key via a timing side-channel attack because it relies on the scalar-multiplication implementation in Go crypto/elliptic, which is not constant time (there is an if statement in a loop). One

How urgent is CVE-2023-26556?

Priority 51/100. Critical severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2023-26557 HIGH 7.5 UPGRADE io.finnet tss-lib before 2.0.0 can leak the lambda value of a private key via a timing side-channel attack bec
CVE-2022-47931 CRITICAL 9.1 UPGRADE IO FinNet tss-lib before 2.0.0 allows a collision of hash values.
CVE-2022-47930 MEDIUM 6.8 UPGRADE An issue was discovered in IO FinNet tss-lib before 2.0.0

References

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