SSH server timing side-channel in ssh_auth:check_password/3 allows unauthenticated username enumeration
Severity and exploitation
KEV coverage does not rule out exploitation.
Assessment vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:NSeverity
medium6.3CVSS measures technical severity, not the likelihood of an attack.
Known exploitation
Not listed in the checked CISA KEV catalog
Absence from CISA KEV does not rule out attacks.
Public exploit
Not established by this record
Missing evidence does not mean no public exploit exists.
Remediation
Source guidance available
Review the recorded instructions. Guidance may be a workaround rather than a fixed version.
What this means
Erlang/OTP ssh versions 29.0 before 29.0.2 and 6.0 before 6.0.1 have an Observable Timing Discrepancy vulnerability, allowing unauthenticated remote username enumeration via a timing side-channel in password authentication. An attacker with network access can exploit this weakness. The impact is limited to username enumeration.
Summarized by @cf/meta/llama-3.3-70b-instruct-fp8-fast. Verify details against the original sources.Attack conditions
No attack-condition excerpt has been identified here. Review the full source description and references for authentication, network access, and configuration requirements.
Review supporting sources →Affected versions
Check the exact model, release, and any platform requirements against your installation.
Erlang · EEF
OTP
1 range
Erlang · EEF
OTP
Package identity
pkg:software-id/erlang.org/otpIdentity supplied by EEF. Version matching requires compatible range evidence.
Compare with this publisher’s ranges. This does not inspect your installation.
affected
29.0 → before 29.0.2
otp versions
Other versions: unaffected
Product identifiers (CPE)
cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*Erlang · EEF
OTP
1 range
Erlang · EEF
OTP
Package identity
pkg:otp/ssh?repository_url=https:%2F%2Fgithub.com%2Ferlang%2Fotp&vcs_url=git%2Bhttps:%2F%2Fgithub.com%2Ferlang%2Fotp.gitIdentity supplied by EEF. Version matching requires compatible range evidence.
Compare with this publisher’s ranges. This does not inspect your installation.
affected
6.0 → before 6.0.1
otp versions
Other versions: unaffected
Product identifiers (CPE)
cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*Erlang · EEF
OTP
1 range
Erlang · EEF
OTP
Package identity
pkg:github/erlang/otpIdentity supplied by EEF. Version matching requires compatible range evidence.
Compare with this publisher’s ranges. This does not inspect your installation.
affected
032d1bc9491a3975c68faf9bc7776115d6ae3005 → before c342092ef4b369bb409d5b71ac8fd83bab74aedf
git versions
Other versions: unaffected
Product identifiers (CPE)
cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*What to do
Compare your installed product and version with the affected versions above. A matching product name alone does not confirm exposure.
- Use the pwdfun option instead of user_passwords for password authentication. The pwdfun callback gives full control over timing behavior and is not affected by this vulnerability. Implementations should take care to execute in approximately constant time regardless of username validity.
- Restrict SSH port access to trusted networks only via firewall rules, reducing the set of potential attackers who can perform timing measurements.
cve.new guidance unless attributed to a publisher. This page does not inspect your installation.
Public exploit evidence
No public exploit reference is identified in the imported evidence. This is not a claim that no exploit exists.
Original source description
Read the full publisher description
Observable Timing Discrepancy vulnerability in Erlang/OTP ssh (ssh_auth, ssh_options modules) allows unauthenticated remote username enumeration via timing side-channel in password authentication.
When the SSH daemon is configured with the user_passwords or password option, ssh_auth:check_password/3 performs a PBKDF2-SHA256 computation with 600,000 iterations (~300ms) for valid usernames, but returns immediately (~0ms) for invalid usernames via the ssh_options:get_password_option/2 path. This timing difference is detectable in a single authentication attempt and allows an unauthenticated attacker to distinguish valid from invalid usernames.
The user_passwords and password options are documented as intended for test purposes; the recommended alternative is pwdfun, which is not affected by this vulnerability.
This vulnerability is associated with program files lib/ssh/src/ssh_auth.erl and lib/ssh/src/ssh_options.erl.
This issue affects OTP from OTP 29.0 before OTP 29.0.2, corresponding to ssh from 6.0 before 6.0.1.
References
6 sourcesInside the record
Evidence available
Describes the evidence in this view, not whether the product is safe.
Original records
CVE-2026-48859View the latest unmodified CVE JSON from the official source. It may be newer than this imported page.
cve.new JSON →Underlying weaknesses
The source’s classification of what caused the vulnerability.
Environment requirements
These conditions apply together as specified by the publisher. A matching product name alone does not establish exposure.
EEF · platform conditions
All conditions must hold
Any condition may hold
Vulnerable product
cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*From (inclusive): 29.0
Before: 29.0.2
Applicability preview
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"criteria": "cpe:2.3:a:erlang:erlang\\/otp:*:*:*:*:*:*:*:*",
"versionEndExcluding": "29.0.2",
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]Contributing organizations · 2
Assigning organization
Additional data publisher
Timeline
All times UTCAdvisory published
Publication date supplied by the source.
Source updated
Latest modification date supplied by the source.
Last imported by cve.new
Latest catalog import, not the date we first saw this advisory.
What changed
Follow changesLarge field values are marked as truncated previews. Original source snapshots remain retained.